The remains of dirty North African pots dating back 10,200 years have just yielded the first known direct evidence for cooked vegetables, grains and other plant products.

The prehistoric cooked food remains are so old that they predate plant domestication and agriculture in the region by at least 4,000 years, according to a new study in the journal Nature Plants.

Animal fats known as lipids were also found on the ancient ceramic vessels.

The evidence indicates the foods included "grains cooked to make porridge-type dishes that are very common in Africa even today," and boiled "leafy plants, sedges or aquatic plants" that were likely mixed with meat and/or animal fats, lead author Julie Dunne, a post-doctoral research associate at the University of Bristol School of Chemistry, told Seeker.

She and her team made the determinations after studying the unglazed pottery, which was found at two sites in the Libyan Sahara: Takarkori and Uan Afuda. At the time of pottery's use, the sites were part of a green savannah characterized by coarse grasses and scattered tree growth.

Chemical signatures taken from the pottery show that a wide variety of plant products were being cooked back in the day. These included parts of fig trees, cattails, cypress, burr or carrot seed grass, cassia and desert date. Also found at the site were millet, foxtail grass and barnyard grass and its fruits. Fruits from Echinochloa, Panicum and Setaria were additionally discovered.

Photo: Botanical remains including leaves, fruits and grains found at the Takarkori rock shelter. (Details on page 2 of the paper, underneath Figure 1.) Credit: The Archaeological Mission in the Sahara. Sapienza University of Rome

The people from this region clearly knew what they were doing, reflecting probably hundreds and perhaps thousands of years of experience in knowing what is good to eat and what tastes lousy or is even poisonous. Most Cupressus (cypress) trees have poisonous parts, for example, so an incredible amount of trial and error must have occurred before certain foods became a regular part of their diet.

Grindstones dating to even earlier times have been found in North Africa. They suggest that plant products were processed and heated for eating earlier than 10,200 years ago, but the new study provides the first direct evidence for cooking.

It's thought that pottery was independently invented twice during human history: first in East Asia around 16,000 years ago, and more recently in North Africa at around the time that the food-encrusted pots were used.

The invention marked a breakthrough. As Dunne explained, "the ability to boil plants for long periods of time in newly invented ceramic vessels would have significantly increased the range of plants prehistoric people could eat."

The food might have been soft enough for infants, she and her team point out. If babies were able to eat the cooked foods, then this could have led to earlier weaning and shorter times between births, thereby enhancing the fertility of women in early pastoral communities.

Cooking veggies and other plant products preceded the emergence of agriculture in the region probably because the people in North Africa did not need to bother with the extra work and trouble. The researchers point out that the "Green Sahara" occupants had plenty of wild game, aquatic resources and plants around them.

Things began to change in the Libyan Sahara around 5,000–6,000 B.C., however, when cattle and other animals started to be raised for their dairy products. Some early ceramic vessels reveal that the latter were cooked too and sometimes with plant products, such as for porridge.

The climate of the region promoted a more mobile lifestyle, "moving the animals in search of food and water," Dunne said.

She suspects that as the region gradually became more arid, the drier conditions could have driven the hunter-gatherers to domesticate plants, instead of just gathering them in the wild.

The timetable for the first plant domestication and agriculture was different in the Near East. There, plants and animals were both domesticated at about the same time: 8,000–9,000 B.C. The spread of farming across Europe followed.